The number of voltages required in a typical communications or server application is rising and seems to average more than five. Furthermore, the required voltage levels are dropping and need to be independently and tightly regulated. There are presently two broad approaches. First, there is the ac “front-end” or dc “bus converter” combined with separate non-isolated “point of load” (or “niPOL”) regulators, usually synchronous buck converters, for each output voltage. The latter part of this approach is often termed the “Intermediate Bus Architecture.” Second, there is the Isolated Converter Module approach that has multiple magnetically coupled outputs, some of which may be post regulated. For both of these approaches the component count is high, with multiple magnetic windings or cores, and usually two isolated pieces of power switch silicon per output. Furthermore, there is the technical obstacle, that, as voltages migrate lower, it is increasingly difficult to employ magnetic coupling alone, as the most cost sensitive applications have relied upon to date. Accordingly, there exists a need for a power conversion approach that generates multiple independently regulated output voltages using a single magnetic and only one switch per additional output.
Several methods of multiple output, single inductor switch-mode topologies have been proposed to address this problem. Practical implementation of these methods, however, is faced with significant difficulties due to complex control methods and bi-directional blocking capability required by the power switches.